The Boston FBI SWAT team arrested former Stoughton Police Officer Matthew Farwell and charged him with allegedly killing Sandra Birchmore, a woman he is accused of having sex with since she was a minor.

“FBI Boston’s SWAT Team has arrested former Stoughton Police Officer Matthew Farwell for allegedly killing Sandra Birchmore. We took him into custody without incident,” the agency tweeted on X a little before noon. The post added that additional information would be revealed at the federal courthouse in Boston at 1:45 p.m.

Prosecutors allege that Farwell on or about Feb. 1, 2021, strangled Birchmore to death, according to a short indictment filed in U.S. District Court in Boston.

Birchmore, of Canton, was born in 1997 and in March 2010, at the age of 12, Birchmore applied to be a participant in the Police Explorer’s Academy, a youth program run by the SPD for which Farwell taught. She stayed in the program for about four years.

Prosecutors allege Farwell began raping the girl before she was 16.

Birchmore found out she was pregnant in December 2020 and told Farwell that he was the father of the child. The next month, one of Birchmore’s friends called the police department to report what Farwell had allegedly been doing, but, according to the indictment, a police department employee tipped Farwell off to the complaint.

Birchmore would die less than two weeks later. Prosecutors allege in the indictment that Farwell staged Birchmore’s apartment to look as though she had committed suicide.

Farwell worked at the SPD between March 2012 and April 2022, according to the indictment. He worked as an instructor for the Police Explorers program since he began with the department.

Stoughton Police Chief Donna McNamara said in April 2022 that the department first heard of the allegations in February 2021 and placed Farwell on administrative leave, “the strongest action allowable by law for the town at that time,” that month as it launched an internal affairs investigation. Farwell submitted his resignation that April.

This is a developing story.